1. Field of the Invention
The present invention relates to a single-focal-length imaging lens system that is applicable to an imaging optical system, particularly, an interchangeable lens or a digital still camera.
2. Description of the Background Art
With the growing popularity of cameras, lenses of various specifications have been proposed. Prior art documents proposing lens systems having F numbers ranging from about 1.4 to 2.4 are as follows: Japanese Laid-Open Patent Publication No. 63-96619, Japanese Laid-Open Patent Publication No. 2-23309, Japanese Laid-Open Patent Publication No. 8-171050, Japanese Laid-Open Patent Publication No. 2000-19393, and Japanese Laid-Open Patent Publication No. 2002-250863.